--- qemu/hw/usb-bus.c	2018/04/24 17:37:33	1.1
+++ qemu/hw/usb-bus.c	2018/04/24 18:28:27	1.1.1.3
@@ -102,6 +102,9 @@ USBDevice *usb_create(USBBus *bus, const
 USBDevice *usb_create_simple(USBBus *bus, const char *name)
 {
     USBDevice *dev = usb_create(bus, name);
+    if (!dev) {
+        hw_error("Failed to create USB device '%s'\n", name);
+    }
     qdev_init_nofail(&dev->qdev);
     return dev;
 }
@@ -149,11 +152,10 @@ static void do_attach(USBDevice *dev)
 int usb_device_attach(USBDevice *dev)
 {
     USBBus *bus = usb_bus_from_device(dev);
-    USBDevice *hub;
 
     if (bus->nfree == 1) {
         /* Create a new hub and chain it on.  */
-        hub = usb_create_simple(bus, "usb-hub");
+        usb_create_simple(bus, "usb-hub");
     }
     do_attach(dev);
     return 0;
@@ -261,7 +263,8 @@ USBDevice *usbdevice_create(const char *
     USBBus *bus = usb_bus_find(-1 /* any */);
     DeviceInfo *info;
     USBDeviceInfo *usb;
-    char driver[32], *params;
+    char driver[32];
+    const char *params;
     int len;
 
     params = strchr(cmdline,':');
@@ -272,6 +275,7 @@ USBDevice *usbdevice_create(const char *
             len = sizeof(driver);
         pstrcpy(driver, len, cmdline);
     } else {
+        params = "";
         pstrcpy(driver, sizeof(driver), cmdline);
     }
 
@@ -288,14 +292,14 @@ USBDevice *usbdevice_create(const char *
     if (info == NULL) {
 #if 0
         /* no error because some drivers are not converted (yet) */
-        qemu_error("usbdevice %s not found\n", driver);
+        error_report("usbdevice %s not found", driver);
 #endif
         return NULL;
     }
 
     if (!usb->usbdevice_init) {
-        if (params) {
-            qemu_error("usbdevice %s accepts no params\n", driver);
+        if (*params) {
+            error_report("usbdevice %s accepts no params", driver);
             return NULL;
         }
         return usb_create_simple(bus, usb->qdev.name);